Improvement in slide-valves for



Ntra STATES PATENT raten.

A. J. STEVENS, OF SAlNT FRANCISCQCALIFORN IA.

IMPROVEMENT IN SLIDE-VALVES FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 39,181, dated July 7,1863; antedatezl April 29, 1863.

To all, whom t may concern:

Be it known that I, A. J. STEVENS, of the city of San Francisco, in thecounty of San Francisco and State of California, have invented a new anduseful Improvement in the Slide-Valves of Steam-Engines; and I do herebydeclare that the following :is a full, clear, and exact description ofthe same, reference being had to the accompanying draw ings, formingpart of this specification, in which- Figure 1 is a longitudinalvertical section of the valve chest and slide-valve of a steam, enginewith my improvement applied. Fig. 2 is a plan of the same with the coverof the chest and follower of the valve removed.

Similar letters of reference indicate corresponding parts in the twofigures.

This invention relates to the employment, in combination with theslide-valve of a steamengi11e,of what I have termed, in a patent grantedto me June 1S, 1862, an anti-coinpression valve 7 for preventing thecompression of the steaml in the cylinder on the eX- haust-side of thepiston after the port has been closed by the lap on the inside of thevalve, as is the case when the valve has a long lap.

The object of 011e part of the invention is to dispense with anymechanism for operating such a valve; and to this end it consists in thesubstitution for a single anti-compression valve oftheslidingkind of twopuppet-valves, so applied as to be operated upon directly by the steamin such manner as to produce the desired result.

Another part of the invention consists in an improved mode of applying afollower in coinbination with the main valve and anti-compressionvalves, to serve the double purpose of protecting the back of the mainvalve from the pressure of the steam to such an eXtent as may bedesired, and to form a means of communication between theanticompression valve-chest and the atmosphere or exhaustpipe of theengine.

To enable those skilled in the art to make and use my invention, I willproceed to describe its construction and operation.

A is the valve-chest of the engine.

a a are steam-ports, and b the exhaust-port, constructed in the mannercommon to engines using a single short slide valve.

B is the slide-valve constructed like an ordinary short slide-valve,except that it has two passages, c c', right through it, like thatdescribed in my Letters Patent hereinbefore mentioned, and has formedall round its back a ange, d, which stands up perpendicular to its facefor the attachment of the follower (l, the manner of whose applicationwill be presently described.

D is the anttcompression valve-chest having two separate chambers, e e',each of which covers the outer oritice of one of the passages, c c', anda central cavity, d, between the said chambers, the said cavity beingopen at the back.

g g are the anti-com pression valves, of which there may be two ormore-viz., one or more for each of the passages c c. These valves are ofthe puppet kind and fitted to seats formed in openings z' t', which formmeans of communication between the chambers c e and central cavity, d,and the said openings are formed opposite each other, and two valvesbelonging to opposite openings are secured together face to face asrepresented'in Fig. l, by attaching both to the same stem. The saidvalves work on fixed guide-pins n u, screwed into the sides of the chestD. The chest D is secured to the back of the main valve B by means ofbolts fj'.

The follower C is composed of a frame fitted snugly to the exterior oftheliange d, and having a flange, h, all round it fitting to the flatinner surface of the cover A ofthe main valvechest A, such surface beingparallel with the main valve-seat. Around the exterior of the rabbet forthe reception of a packin g, j, of india-rubber or other material, andof a gland, E, which is fitted around that portion of the is screweddown upon the packing to make a steam-tight joint between the main valveand the follower by means of nuts l l, tting to screwed pins lc k, whichare screwed tightly into the main valve and pass through lugs in theinterior of the gland. These nuts are reached when it is desirable toscrew down the packing by the removal of -a plate, F, which is securedto and covers an opening, m m, in the valve-chest cover A.

l G is a spring applied to the follower C, and

upper part of the iiange el there is formed a iiange and within thefollower (l. This glandresting upon the top of the anti-compressionvalve-chest D, for the purpose of holding the follower up to its seat onthe inside of the cover A when the engine is not at work and ofpreventing it from being drawn down by the act of screwing down thegland. The tension or pressure of this spring is regulated by aset-screw, p, screwing through the spring and pressing on the top of theanti-compression valvecl1est G. When the engine is at work, the followeris held in contact with the plate A `by the pressure of steam on itsflange h, and it protects from pressure the whole of the back of themain valve, with the exception of its marginal portion. H is anexhaust-pipe forming a means of communication between the space withinthe follower C and the main exhaust-pipe ofthe engine or the atmosphere.The main valve B is operated in the usual manner, and during itsmovement, as soon as it closes either port a or a to the steam, one ofthe passages c or c arrives over that port and t team rushes from thecylinder through the said passage into its respective chamber e or e',and by its pressure on the valveg org of that chamber closes that valve,and so opens the opposite one g or gf, so that after the other port a.or ce is closed to the exhaustport b and its respective passage c or carrives over that port the exhaustion of the steam from the cyl inder iscontinued through that port, through the chamber e or e and open valve gor g, through the space d and the space within the follower', and hencethrough the pipe hv, and the compression of the steam on the exhaustside of the piston is prevented. This is illus .trated in Fig. l, inwhich the valve is supposed to be moving to the left, and steam has beencut oft' from the port a., and the port a' has been closed to theexhaust by the lap on the inside of the valve, but steam passing fromthe cylinder through the port a and passage c into the chamber e hasclosed the valve g, and thereby opened g', and the exhaust of the steamfrom the port a is permitted to be continued through the passage c',chamber e', valve g', and passage d, and through thefollower U and pipeH. When the piston moves in the opposite direction, the operation isprecisely the reverse of that above described. The follower, it will beperceived, serves not only the purpose of protecting the back of thevalves to a desirable extent from the pressure of the steam, but as ameans of ci mmunication between the anti-compression valves and theexhaust-pipe or atmosphere.

What I claim as my invention, and desire to secure by Letters Patent,is-

l. The connected puppet-valves g g', applied, in combination withseparate chambers e e', and in relation to the main valve, substantiallyas and for the purpose herein specified.

2. The follower G, combined with the valve by means of an internalgland, E, and otherwise applied as herein specified, to serve not onlyfor the protection of the back of the valve from the pressure of steambut as a means ot' communication between the anticompression valve-chestand the exh aust-pipe or atmosphere, as herein set forth.

A. J. STEVENSV Witnesses M. T. DUsINBURY, A. M. BoYLn.

